Patent Literature 1 discloses an oil level regulating apparatus for a piston jet. As shown in FIG. 1 of this literature, the oil level regulating apparatus includes a valve unit and a solenoid unit. The valve unit and the solenoid unit are disposed separately from each other. The valve unit and the solenoid unit are axially perpendicular to each other.
An engine is provided with an oil channel. The oil channel is provided with a piston jet path and a pressure introducing path. The valve unit includes a valve configured to open and close the piston jet path. Specifically, the piston jet path can be opened if the valve is shifted to the rear side. In contrast, the piston jet path can be closed if the valve is shifted to the front side.
The valve has a front surface that receives pressure (supply pressure) of oil from the piston jet path. The valve has a rear surface to which pressure (control pressure) of oil is introduced from the piston jet path through the pressure introducing path. The pressure introducing path is opened and closed by a shaft of the solenoid unit.
When the shaft opens the pressure introducing path, supply pressure is applied to the front surface of the valve whereas control pressure is applied to the rear surface of the valve. The supply pressure and the control pressure are balanced in this state. The supply pressure and the control pressure accordingly offset each other. The valve unit is provided with a spring biasing the valve toward the front (so as to be closed). The valve accordingly closes the piston jet path with biasing force of the spring. The piston jet is not supplied with oil in this case.
When the shaft closes the pressure introducing path, supply pressure is applied to the front surface of the valve. However, no control pressure is applied to the rear surface of the valve. In this case, the valve is shifted depending on the magnitude correlation between the biasing force of the spring and a load of the supply pressure. The piston jet path is opened if the load of the supply pressure is larger than the biasing force of the spring. The piston jet is thus supplied with oil in this case.